This project is concerned with the structure and assembly of chromatin, particularly at the level of the histone octamer which forms the core structure of nucleosomes. Contact sites, important in forming and maintaining nucleosomal structure, will be identified in the octamer and its components. These contact sites and any changes that occur in them will be used to assess conformation changes that may occur during nucleosomal assembly, postsynthetic modification and other processes that may affect chromatin functions by changing chromatin structure. Zero-length crosslinking, chemical and enzymic modifications, circular dichroism and other chemical-physical techniques will be used in these studies.